Exercise equipment is widely used by individuals at home and in a spa setting to obtain both strength and aerobic exercise. From free weights, strength training has now progressed to typically include the use of one or more exercise machines for greater ease of use and safety. For example, U.S. Pat. No. 3,858,873 to Jones, and assigned to the assignee of the present invention, discloses cams to provide nonlinear resistance compatible with that developed by human joints and muscles.
Aerobic classes have enjoyed widespread popularity for aerobic training of the cardiovascular system. In addition, aerobic exercise machines have also been developed, such as, for example, stationary bicycles, rowing machines, and, most recently, stair stepping machines. Stair stepping machines are particularly popular for toning the muscles of the lower body and providing an excellent aerobic workout.
A typical stair stepping exercise machine includes two foot platforms which the user alternately depresses by shifting his body weight and straightening the respective leg, thereby performing a simulated stair climbing exercise. The foot platforms are connected to a load to provide resistance to the user's stepping motion. For example, U.S. Pat. No. 3,747,924 to Champoux discloses a stair stepping machine with interconnected foot platforms so that the load on one foot platform is provided by the use's weight carried by the other foot platform. U.S. Pat. No. 4,708,338 to Potts discloses a stair stepping machine with an electrical alternator and resistor to provide the load for the user. U.S. Pat. No. 4,720,093 to Del Mar discloses a stair stepping machine having a flywheel and friction band to provide resistance. U.S. Pat. No. 4,949,993 to Stark discloses a stair stepper with independently operable foot platforms wherein the resistive load is provided by a spring. U.S. Pat. No. 5,033,733 to Findlay discloses a stair stepper with an electromagnetic brake to provide the resistance for the user's movement. Regardless of the approach to providing resistance, it is desirable that the resistance be controllable and smooth to prevent possible injury to the user.
The conventional stair steppers discussed above also each include foot platforms that remain generally horizontal throughout the user's stepping motion. This arrangement requires that the user sharply bend both the ankle and the knee joints. Unfortunately, such an arrangement is likely to create stress on the ankle joint and lower leg, and, more particularly, such an arrangement is likely to create undesirable shear forces on the knee joint.
For stair steppers, like other stationary exercise machines, it is also desirable to provide the user with feedback concerning the level of effort and performance. For example, U.S. Pat. No. 4,708,338 to Potts discloses a display of vertically oriented lights indicative of the varying level of resistance versus time for the exercise period. While such a visual display provides some feedback to the user, it does little to relieve any boredom that may result during an extended exercise period.